Electrical discharge device



March 21, 1933. K. B. McEAcHRoN Er AL 1,902,510

ELECTRICAL DISCHARGE DEVICE Filed Jan. 2o, 1932 Inventors I Karl B, McEeLchr`o1-1,

Elms-:r J. Wada Their Attorney Patented Mu. 21, 1933 UNITED sTATEs PATENT OFFICE KARL B. MCEAQHBDN' AN D ELHER J'. WADE, 0F PITTBFIELD, .MASSACHUSETTS vASSIGN- ORS T0 GENERAL ELECTRIC CMPANY, A CORPORATION OFNEW 'YORK ELECTRICAL DISCHARGE DEVICE Application med January 20, 1932. Serial No. 587,716.

Our invention relates to electrical discharge devices such as are used for protecting electrical transmission lines and apparatus from excess voltages. More particularly,

5 the invention relates to an electrical dis-a charge device provided with a series of spark gaps with means for distributing an applied normal voltage in a predetermined manner between the gaps under normal operating conditions and for disturbing this voltage distribution when an abnomal voltage is applied to cause the gaps to break down.

The invention will be better understood from the ollowingdescription taken in connection with the accompanying drawing in which Fig. 1 is a view of a discharge device constructed in accordance with the invention, the parts of the device being separated to show the construction more clearly; Fig. 2 is a sectional view of the discharge device with the parts assembled; Fig. 3 is an er1-- planatory, perspective view of a detail of the construction; Fig. 4 is an inside view of the base of the casing; Fig. 5 is a view of the bot tom of the casing; Fig. 6 is a sectional view of a spark gap assembly; Fig. 7 is a dia rammatic view of the electrical circuits, an Fig.

8 is a diagrammatic view of two units connected in series betweenl a line and ground. Like reference characters indicate similar parts in the above gures of the drawing.

The discharge device as shown in thedrawing includes a casing having a base portion 1G and a cover 11 formed of insulating material such as porcelain. The base and cover are fitted together with an interposed gasket 12 to keep out moisture. A curved strip of resistance material 13 is supported in the cas ingy by a pluralityr of conductive springs 14, the lower ends of the sprin s restlng in de= pressions in the base 10 an the upper ends of the springs being connected to screws 15 extending through the resistance strip 13. A terminal 16 is secured to the up er surface of the resistance strip 13 by each o the screws 15. A spark gap assembly 17 is inserted between each adJacent pair ,of terminals 16 and held in place by a s ring 18.

The lower end o each sprin 14( rests on a conductive coating 19 in the ottom of the corresponding depression in the basel. A conductive coating 20 is applied to the outer surface of the base 10 opposite all of the inner coatings 19. One of the end terminals 16 is provided with a projection 21 which extends through an opening 22 in the cover 11 and the other end terminal 16 is provided with a projection 23 extending through an opening 24 in the base 10, these projections 21 and23 serving as terminal connections for the discharge device. The base 10 and cover 11 are held tightly together by a bolt 25, the 'inner surface of the cover pressing on the gap assemblies 17 to hold these gap assemblies and the resistance strip 13 and springs 14 in place.

With the construction which has been described, a section of the resistance strip 13 is connected in parallel with each of the gap assemblies 1'? and each of the terminals 16 is electrically connected to the conductive coating 2O through its spring 14 and the capacity betweenfthe corresponding inner coating 19 and the outer coating 20. This outer conductive coating 2O is connected to a ground 26 and in some cases it may be desirable to connect the coating 20 to the ground 26 through a resistance 27.

The resistance strip 13 has a very hi vh resistance so that the leakage-current un er normal operating conditions will be very small. The current through this resistance 13, however, at normal operating frequency will determine the distribution of' voltgp across the several gap assemblies 17. e capacities between the coatings 19 and 20 are so small that at normal operating frequency.

the current to ground through these capacities from the terminals 16 is negligible and has no appreciable effect on the distribution of voltages across the gap assemblies. The

current through these capacities, however,-

Y series of gaps the capacity current will predominate un er steep Wave :front or high fre uency conditions and result in a nonuniciormdistribution of voltage to cause rogressive breakdown of the gaps. There ore, when a voltage having e steep yvvave iront or high requency is applied across the terminals 2i and 23,' the distribution ci volta e between the ga assemblies is determined y the capacities Eetween the coatings i9 and 20. The voltages necessary to break down the gaps between the gap assemblies are proportional to the respective gap settings and Wiii therefore all be equei ii the gap settings are equal. The values of the capacities between the coatings 19 and 20 are iarge as compared with the capacities across adjacent gaps so that the currents through these capacities under high :frequency conditions wili be comparatively lar e so as to determine the high frequency vo tage distribution `loetvveen the ap assemblies.

here the operating voltage is higher than that for which a single unit, such as has been-described, is designed, a pluialiiy of units may be connected in series es indicated diagianimaticaliy in Fig. 8.

The invention has been explained by describing and iliustreting a particuier forni ci? the invention, but it Wili be apparent inet chen es ma be made Without dcneifizins"y Leoncio 'including said cover for lholding said gap assemloiies in place in said casing.

and the inner surface of said in Witness whereof, We have hereunto set our hands.

KARL B. MCEACHRON.

ELE/ER J. WADE.

irom 'the spirit ci the invention and the scope n of the appended claims.

What We claim as nevv end desire to secure by Letters Patent of the United States, is,im

i. An eiectricai discharge device inciuding an insuieting casing, a piurality ci? gags assemblies in said ceasing, a support ior seid ,gap assemlaiies, spriny s between said support and the inner* surace ci said casing and connected to said gap assemblies, a conductive f member between each spring and the inner surface of said casing, and a conductive inem bei on the cuter surface of said casingand extending opposite aii of said inner conductive members 2. An eiectricai discharge device inciuding an insulating casing havingv e bese and a cover, a plurality of gap assemblies in said casing, a support for said gap asseniioiies, springs-between said support and the inner surface ci said base and connected to said gap assemblies, a conductive member between each sprin and the inner surface ci? said bese, a con uctive ineber on the outer surface of seid base and extending opposite ail of seid inner conductive members, andmeens for holding said cover against said gap assemblies to heid them in place in said casmg fr.

3. An electrical discharge device includ ingan insulating casing having a bese und a cover, a plurality of gap assemblies in said casing, a support'for said gap assemblies, springs between said support and the inner yes 

